The present invention relates to a method and apparatus for drying substrates such as silicon wafers, and more particularly to a method and apparatus for gently heating a meniscus formed at the transition between the substrate surface and a rinsing liquid upon removal of the substrates from the liquid to produce a temperature gradient between the region of the meniscus along the contact line and the adjacent rinsing liquid and thereby induce thermocapillary flows of the liquid away from the substrates.
Prior to the present invention, methods and apparatus have been proposed for drying substrates after treatment in a rinsing liquid. According to one such method, substrates are treated for a period of time in a bath containing the rinsing liquid, and the substrates are then removed so slowly that practically the entire liquid remains within the bath. In so doing, the substrates are brought directly from the liquid into contact with a vapor. The vapor does not condense on the substrate and mixes with the liquid whereby the mixture has a lower surface tension than the liquid. This method, however, is complicated in practice because vapor is required and the vapor must be removed. Supply lines and exhaust nozzles for the vapor must be made available.
These vapors and in some instances chemicals function to reduce the surface tension of the rinsing liquid. One such approach is the Marangoni drying process which uses small amount of isopropyl alcohol as a surfactant to induce a Marangoni flow away from the solid-liquid contact line to achieve drying.
From U.S. Pat. No. 4,722,752 a device and a method for cleaning and drying of disc-shaped substrates, for example, semiconductor wafers, is known in which the substrates are slowly removed from hot water that serves as a rinsing liquid whereby the surface tension at the transition between the surface of the hot water and the substrates has the effect that the water is removed from the surfaces of the substrates.
U.S. Pat. No. 4,920,350 discloses a device and a method for cleaning substrates where energy in the form ultrasound is supplied to the substrate at the surface of the rinsing liquid upon removal of the substrate from the liquid. The supplied energy serves a function unrelated to drying.